Drilling 304 Stainless

I may have asked this before, but I'm slow:
I have some 304 sheet. I use it to make control-line model airplane handles. Each handle needs to have about 20 1/16" or .050" holes drilled
in it, in a pair of tidy lines.
This stuff breaks my regular old HSS drill bits, and my drill hand- sharpening mojo is pretty spotty at 1/16".
I'm using them in a drill press. The whole process feels weird -- it feels like there's a skin on the metal which prevents the drill from starting to cut unless I feed it fairly hard, but once broken through doesn't cause much problem. Most of the time that I break a drill bit it's because I'm feeding it "just a bit harder", then SPING -- I've broken another bit.
Is there a better drill bit to use, or have I just doomed myself to trouble? Is there a better flavor of _stainless_ to use? I understand that 304 is difficult to work with, but it's what McMaster had in the thickness I wanted; having experienced its joys, however, I'm ready to consider something else.
I think my next step is to get a dozen 1/16" drill bits, but if there's some magic material that'll help here, I'm listening.
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Are you center-punching the holes before drilling?
If so, there IS a "skin" to break through... you've work-hardened the piece where it's punched.
A better strategy is to use a really short bit, and just drill.
LLoyd
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On 2012-08-31, Lloyd E. Sponenburgh <lloydspinsidemindspring.com> wrote:

    And, to prevent it walking, best is to get split-point drill bits. (I might get by preference cobalt steel split point bits in screw machine length, since you don't need the longer flute length of jobber's length bits.
    An alternative to the split points (or perhaps just something to use in *addition* to the above) would be to put down a layer of masking tape, which makes it easier to keep a bit from walking when it starts.
    Good luck,         DoN.
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Perhaps you could hone a very fine split point on the drill? That's tiny but could be done with a small diamond file and a steady stroke. It's worth a try.... pdk
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On 8/30/2012 7:59 PM, Tim Wescott wrote:

304 SS is junk stainless, but cheap. The reason it's so hard to cut is an absence of sulphur in the alloy for lubrication. You have to get the speed & feed just right to cut it, and you still get short tool life. A few more pennies spent on a better alloy will save a lot in tooling.
Or have the parts cut on a LASER, we cut 304 all day long and the LASERs don't wear out!
David
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On Thu, 30 Aug 2012 20:22:29 -0500, David R. Birch wrote:

Kinda spendy for one-offs. I know a guy who laser cuts balsa -- maybe I'll see what kind of price he'd give me for making a handful of the metal parts, assuming he wants to and can.
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On Thu, 30 Aug 2012 23:07:44 -0500, Tim Wescott

Ahh, "A Handful" at a time is not a one-off. How many of these do you sell in a year?
And are there other things you're doing manually now, like hogging out the hand-hole D with a series of finger-grip bumps on the outer edge? The laser can punch that hole at the same time, even make it serrated for a better grip wearing gloves - or so the Caterpillar Grommet padding doesn't slip if they want a fat vinyl edge to grab.
You have a minimum charge for the computer code setup to laser-cut these control-line handles out of sheet, you own that. Then there's another minimum charge for the run time on the laser and cutting table.
If you run off 50 or 100 handles at a shot and use 2 or 3 full sheets, that's probably enough to meet the minimum charges. Should drop the unit cost to where it's silly sitting there with a drill press making them by hand...
And it's All Done - you put in raw stock and get fully finished pieces out of the laser table, if they turn down the power on the laser they can etch the Product Name, Logo, company name and phone number, and the serial number of each handle (auto-sequenced as they are made) easy-peasy. Saves you a label or a screen printing step, and the markings are indelible.
They just need a touch of deburring at the start point and a quick passivation & wash, final inspection, then wrap 'em up. And when the stock gets low and orders are still trickling in, you do it again.
--<< Bruce >>--
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Blink! Blink!
Junk stainless?
I don't think so.

While I'd agree that a change of alloy would be helpful, to imply that this is an inferior alloy is nonsense. It's no such thing. It simply isn't free machining, as you implied, which has no relationship to its quality.
A free machining grade of stainless, if anything, might be considered a somewhat inferior alloy, as the presence of sulfur (or selenium) tends to lower chemical resistance, although improving machining characteristics immeasurably. I
If the article in question can be fashioned from bar stock, that would be my choice---303 S (or Se) stainless. However, that grade is not available as plate, as it does not lend itself to welding, so there is limited need in that configuration.
Harold
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Forgot, Tim...
Even the drilling must be done apace. If you dawdle or idle in the hole, it will work-harden. You must drill smoothly through in one pass, or at least _instantly_ retract the bit if you must stop before penetrating it.
Some coolant or cutting oil will help preserve your edges, too.
LLoyd
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wrote:

Any reason not to use 6061T6 aluminum instead??? If you NEED to use stainless, you will NEED a better drill bit. With stainless you need a POSITIVE feed - never let the bit skate on the surface. I'd try a good center punch - or use a "center drill" to make the starting dimple, then follow through with the normal bit. Get one of those that they show at tradeshows etc drilling through files and leaf springs, and using them as milling cutters.
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snipped-for-privacy@snyder.on.ca wrote:

303 stainless will machine and drill much better because of the sulfur content of the metal. The bad part is that 303 doesn't weld well because of the sulfur content.
John
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On Thu, 30 Aug 2012 21:58:28 -0400, john wrote:

McMaster doesn't carry it, but I suppose that means I should just look around.
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snipped-for-privacy@seemywebsite.please says...

Actually they do carry it, but possibly not in the size you need. They also have 1/16" carbide bits in several flavors, some specifically intended for stainless and other very hard steels.
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On Sat, 08 Sep 2012 18:00:09 -0400, J. Clarke wrote:

I write "it" meaning "303 stainless in sheets thinner than 1/16 inch".
If you are reading "it" as meaning "any old 303 stainless no matter the dimensions" -- then yes, McMaster's carries it.
But they sure don't have _my_ "it".
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On Thu, 30 Aug 2012 21:50:56 -0400, clare wrote:

Aluminum wears too quickly. The holes are for steel line clips, which must bear the centrifugal force of the airplane at the same time that the handle is being worked.
But it would make the job much easier.
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Just a thought... could/would some sort of hardened bushing/fairlead/lead-out work?
It would make the handle assembly lighter as well
Erik
PS, I also flew a lot of C/L as a kid it was the mid/late 60's...
Combat, rat, and even dabbled in a little jet speed.
The hot handle of those days was red plastic, with a piece of cable threaded through it. The ends of the cable had eyes swaged in with 'Nicopress' like sleeves. Not sure of the name... EZ-Just or EZ-Adjust comes to mind...
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On Thu, 30 Aug 2012 22:43:57 -0700, Erik wrote:

EZ-Just. I have one.
The hot ticket for control line stunt is a hard-point handle of some sort, with no heavy cable to soften the response by acting as a spring. The handle design I'm using uses a line of holes to adjust spacing, and different-sized clips at the handle to adjust the neutral point. It's exceptionally simple -- except for drilling those damned holes.
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So, line the holes with SS grommets/hollow rivets.
It would even "look cool", with the grommets indicating that someone had done something about the wear issue.
Lloyd
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On Fri, 31 Aug 2012 06:09:17 -0500, Lloyd E. Sponenburgh wrote:

The holes need to be spaced 100 mils apart, and the hole in the grommet couldn't be less than 50 mil, and 1/16 is better. So it'd need to be a pretty teeny grommet.
Any suggestions where to find such?
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Tim Wescott wrote:

Stainless POP rivets? Install rivet, pop, hit the back side with a grinder to smooth them off. If you want the back to look pretty use a cupped grinding point to dress them.
Or use the rivet heads and a press to form the back. Could even spin the back side down.
--
Steve W.

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